When testing mobile terminals, both the output power and the receiver characteristics must be tested.
The test equipment should be made as small as possible, for ergonomic reasons and to reduce the space needed for test.
The transmitter/receiver tests may be carried out in different ways. One fundamental problem when testing is to shield the test equipment so that no irrelevant signals disturb the tests. Also, the test signals should not disturb other signalling, for example other tests. Therefore, it will not be possible to perform outdoor tests through the air interface. Shielded rooms and cages may be used, but the shielding material that is required on the walls cause power losses and also increases the size of the equipment.
The most commonly used method today is to connect the outlet of the antenna to the measurement equipment through a co-axial cable. This is only possible if the antenna is removable. Also, this method does not test the function of the antenna itself.